Transverse susceptibility as the low-frequency limit of ferromagnetic resonance

A new theory of transverse susceptibility (TS) based on magnetization vector dynamics, as described by the Landau–Lifshitz equation of motion, is given. It is shown that the traditional TS experiment is, in fact, the zero-frequency limit of the ferromagnetic resonance (FMR). The importance of these results resides in the generality of the approach which allows one to find the TS for virtually any magnetic system if an expression for the magnetic free-energy density is known. Moreover, the effect of the frequency of excitatory AC field on the TS experiments and the effect of energy dissipation through the imaginary part of TS emerge coherently from the new TS model.     

Unconventional large-N limit of the Gaussian effective potential and the phase transition in λφ 4 theory

In the conventional large-N limit the coupling constant is required to scale as 1/N. While the Gaussian effective potential (GEP) is known to contain the exact result in this limit, it shows a phase transition only when 1/N (in units of the renormalized mass in the symmetric vacuum). Here we determine the asymptotic behaviour, asN, of and other quantities at the phase transition of the GEP. We find _crit to be finite in 0+1 dimensions; of order 1/lnN in 1+1 dimensions; 1/N ^1/3 in 2+1 dimensions; and in 3+1 dimensions. The GEP's first-order phase transition is shown to become asymptotically second-order in 1+1 dimensions and below. We also discuss non-integer dimensions and the approach to the non-trivial autonomous theory in 3+1 dimensions.     

Separable single-particle Hamiltonian and its local equivalent

By using a method developed by Coz, Arnold and MacKellar the local equivalent of a single-particle potential discussed in a previous work is constructed and analyzed. The accuracy of the method is checked in the present case. The numerical examples refer to the low-energy elastic scattering of neutrons from nuclei described by a hole in a closed shell. The single-particle bound states are approximately described by harmonic oscillator wave functions. The results are similar to those derived by Coz, Arnold and MacKellar from non-local Hartree-Fock potentials.     

Search for pi(0)-->nu(mu)nu(mu) decays in the LSND detector

We observe a net beam excess of 8.7+/-6.3(stat)+/-2.4(syst) events, above 160 MeV, resulting from the charged-current reaction of nu(micro) and/or nu;(mu) on C and H in the LSND detector. No beam-related muon background is expected in this energy regime. Within an analysis framework of pi(0)-->nu(mu)nu;(mu), we set a direct upper limit for this branching ratio of Gamma(pi(0)-->nu(mu)nu;(mu))/Gamma(pi(0)-->all)<1.6 x 10(-6) at 90% confidence level.     

Size effect in spin-crossover systems investigated by FORC measurements,for surfacted [Fe(NH<Subscript>2</Subscript>-trz)<Subscript>3</Subscript>](Br)<Subscript>2</Subscript>·3H<Subscript>2</Subscript>O nanoparticles: reversible contributions and critical size

We investigated the thermal transition of coated nano-particles of the title compound, on a set of samples of average diameter ⟨d⟩ ~ 30, 50, 70, 110 nm, with rather broad size distributions. As expected, the width of the major hysteresis loop was an increasing function of ⟨d⟩. We recorded first-order reversal curves (FORC), the initial parts of which displayed a finite slope, revealing the presence of reversible contributions expected from particles smaller than the critical size d _C associated with the collapse of the hysteresis loop. Kinetic effects were also evidenced thanks to isothermal stages. Reversibility of the FORC curves at the vicinity of the reversal temperature was controlled. Thanks to the reversibility property we could determine the reversible contributions to the total response of all samples and derive the corresponding d _C values. Consistent results were obtained by accounting for an anhysteretic contribution from the large particles, leading to an accurate determination d _C  ~ 45−50 nm, much better than the width of the size distributions.     

Deterministic and non-deterministic switching in chains of magnetic hysterons

This paper presents a fundamental analysis of a single-domain ferromagnetic particles chain hysteresis in perpendicular geometry as a prototype for ultra-high density memories. Due to magnetostatic long range interactions the system has a complex hysteresis but stable features can be found. The loop has a number of deterministic Barkhausen jumps and consequently a number of stable plateaus that could be used in multistate memories. The fundamental elements that sustain this behavior are shown and discussed.     

Vanishing evaluations of simple functors

The classification of simple biset functors is known, but the evaluation of a simple biset functor at a finite group G$G$ may be zero. We investigate various situations where this happens, as well as cases where this does not occur. We also prove a closed formula for such an evaluation under some restrictive conditions on  G$G$.     

Δπ decay of baryons in a flux-tube-breaking mechanism

Based on the flux-tube-breaking mechanism, we have previously studied the strong decay of nonstrange baryons into the elastic and several inelastic channels. Here, we extend these studies toΔ π decay. We compare our results with those of Koniuk and Isgur and with recently improved experimental data. We also present results of a new and improved calculation ofN π decay and discuss the problem of resonance identification.